Project Summary/Abstract There is an ever growing demand for implantable cardiac defibrillators (ICDs), with over 100,000 devices implanted in 2004, and dramatic increases anticipated over the next decade due to expanded indications and coverage by Medicare. The growing level of acceptance of these life- saving devices has increased the desire for improved ICD function. The lifetime of the average ICD patient after implant has increased to 10 years while the average device lifetime is around 5 years. Thus, most patients require additional surgeries to replace their original device, resulting in both clinical risk and cost. The current benchmark power source technology is lithium/silver vanadium oxide (Li/SVO) developed >20 years ago. Li/SVO battery technology can display a significant midlife decrease in performance termed voltage delay. This voltage delay, a result of cathode solubility and the associated formation of a passivation film on the anode, has caused premature device explants for numerous patients at the 2.5 to 3 year point due to delays in therapy delivery. Along with the added expense of the unplanned surgery, premature device explant can create patient anxiety. Options employed to `work around' Li/SVO voltage delay lead to shortened battery life. The overall project goal is to solve this problem with fundamental science by demonstrating new superior cathode materials that could be used to extend the life and improve the consistency of ICD batteries. The proposed project has three specific objectives: 1) develop a new class of improved battery materials for ICD applications based on metal-metal-phosphorous-oxides of the MwM'xPyOz (MM'PO) family (M = silver or copper; M' = vanadium or iron), 2) test the materials in experimental batteries under simulated use schemes mimicking ICD function, and 3) compare the key characteristics of long term stability (lack of solubility and voltage delay), energy delivery, and energy content with the current battery benchmark technology (Li/SVO). The proposed activity involves the synthesis, characterization and electrochemistry of a new family of materials, MM'POs. We hypothesize that MM'POs will have improved ICD battery performance based on their fundamental chemical properties: reduced solubility of phosphate based materials compared to analogous oxide compounds, high voltage of vanadium or iron compounds yielding high levels of energy delivery, and the inclusion of silver or copper ions in the matrix to provide high volumetric energy content.